run:
1
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at oeis_challenge.A000103.generateGraph(A000103.java:234)
at oeis_challenge.A000103.evolve(A000103.java:302)
at oeis_challenge.A000103.main(A000103.java:322)

The doubly connected edge list (DCEL), also known as half-edge data structure, is a data structure to represent an embedding of a planar graph in the plane, and polytopes in 3D. This data structure provides efficient manipulation of the topological information associated with the objects in question (vertices, edges, faces). It is used in many algorithms of computational geometry to handle polygonal subdivisions of the plane, commonly called planar straight-line graphs (PSLG). For example, a Voronoi diagram is commonly represented by a DCEL inside a bounding box.
This data structure was originally...

@NieDzejkob It may be waaay to late to add that rule :P Besides, the challenge has to end at some point, and if I keep adding rules to prevent that, it'll take the fun away from it for some users: "If he keeps delaying the end, what's the point of continuing?"

@HyperNeutrino You post it, I have to sleep now. https://tio.run/##tVpRc9s2En6WfgXy0EaKZVqyk4datq8eX9pmJmlnLpl78WgykAhLkEhQJUHZake/437Q/bDc7gIgAYpSnLn2wTIF7C6wu98udkEt@YafZmuhlvHqhy9fZLrOcs2WMBqVWibRbZ7z7XtZ6HF3b@7A8LtYKC319hdeLD7wdQvFxxlXSuTjbnddThM5Y7OEFwX7wKVif3Y73c7ZGYsFDOZSzZnYiHyrF/hoyWXBVKYZZ/Msi5mMBR@waanZO7bOs1QWAp4eZZKQIKSEsRJG9UKkEfspy5l44uk6oRH2Np4L9iBFEhdsIXLBikVWJjGbChAnN1wLksNVjOTB/FxoLfIi6nYKzXWlCEkERTr0oMSTHoAosRkw/SjVGCYepOIJk0rD9mIxtqQ9N9An7g4oXUT4nV1XdDsnds1l/iuI7tG3kAWGgUWMmYhwXXjGcWTv5EKXuaq@B@I@we5axOGmnTj7fETcDh0YmOPnnK8XIA/mz169gk/2it0txGwFjszSLF8Dcwrm1I9CgKjHjM2Rox…

well it's not like it's an unfixable problem... it would just make more sense to use a more verbose language now that gets closer to those 104 bytes naturally (or even beyond that) and keep languages like Labyrinth for other problems that need more code anyway.

like Mornington Crescent might be a good idea for the next one

this actually seems fairly doable. 18 is 7 + 7 + 4 (which you can get from Seven Sisters and Heathrow Terminal 4), squaring is built-in, and you can get a 2 from Heathrow Terminal 2. That only leaves the branch for n=0, which shouldn't be too bad though.